How much weight can you lose by fasting for a week?

Answer 1

First i would like to point out that fasting for a week is not recommended as a weight loss method it could be dangerous. When you start to fast the first thing that body will use is it's Glycogen stores, a similar chemical to starch. The body has about 2,000 kcal stored in the muscles and liver. This is broken down to glucose and although only about 500g is stored in the body it also binds about six times it's weight in water so in the first day about 3.5 kg (7 pounds) will be lost. This is the dramatic weight loss that often you see from a crash diet early on. After the glycogen stores are used up then fat burning begins. Fat contains about twice the energy of glycogen for the same weight and no water is bound up with it. If you are moderatly active (But if you are fasting you won't feel like being active) you will use about 2,500 kcal a day which only equates to about 350g of fat a day. The body is a very efficient machine and doesn't take much to power it. So after a week you will lose about 500g of glycogen (1 pound) 3 kg of water (6 pounds) and 2.5 kg of fat (5 pounds) for a total of 6 kg or about 13 pounds. The body will also break down muscle as it needs some protein. It doesn't take long to break down muscle but a lot of effort to put it back. Try exercising more and a few less trips to McDonalds.